1. Technical Field
The present invention relates to a projector.
2. Related Art
In the past, there has been known a projector provided with three reflective light modulation devices such as liquid crystal on silicon (LCOS) for respectively modulating three colored lights of R (red), G (green), and B (blue), a color combining optical device for combining the colored lights respectively modulated by the reflective light modulation devices, and a projection lens for projecting the light beam thus combined (see, e.g., JP-A-2010-008638 (Document 1)).
The projector described in Document 1 is provided with three reflective polarization plates for performing polarization separation on the light beam incident thereto into linearly polarized lights having respective polarization directions perpendicular to each other, three attachment members (support bodies) for supporting the reflective light modulation devices and the reflective polarization plates, and three adjustment members fixed to the color combining optical device and for supporting the support body in addition to the reflective light modulation devices and the color combining optical device.
The adjustment member is provided with a main body attached to a light entrance surface of the color combining optical device, and a pair of arm sections projecting from positions opposed to each other toward the light emission surface in the outer edge of the main body.
The pair of arm sections are each provided with an engaging projection section projecting toward the other of the arm sections.
The support body is formed of a hollow member having a triangular prism shape, and the reflective light modulation device and the reflective polarization plate are attached to the respective side surfaces thereof.
Further, the portions corresponding to the respective bottom surfaces of the triangular prism shape of the support body are respectively provided with engagement receiving sections in which the pair of engaging projection sections are respectively inserted in a loose-fitting manner.
Further, the support body is fixed to the color combining optical device by fixing the engagement receiving section and the engaging projection section to each other with an adhesive in the condition of loose-fitting the pair of engaging projection sections to the pair of engagement receiving sections.
Incidentally, in the case in which the support body is fixed to the color combining optical device (the adjustment member) by curing the adhesive, the support body might be displaced from a desired position due to the contraction of the adhesive when curing. Further, also in the case in which an external force is applied to the projector when the projector is in use, the support body might be displaced from the desired position similarly to the above.
Further, if the support body is displaced from the desired position, it results that the reflective light modulation device is displaced from the position (the design position) where the reflective light modulation device is located at the back focus position of the projection lens, and at the same time, no pixel shift between the reflective light modulation devices exists, and therefore, the pixel shift between the reflective light modulation devices becomes easy to occur.
In particular, in the projector described in Document 1, the support position (fixation position) of the support body with respect to the color combining optical device (the adjustment member) is located in the portion corresponding to each of the bottom surfaces of the support body.
Specifically, the support position is located at the position distant from the center position (hereinafter referred to as a virtual image center) of a light modulation plane (a pseudo light modulation plane) obtained by displacing symmetrically the light modulation plane (the plane on which the image is formed by light modulation) of the reflective light modulation device disposed at the design position in a virtual manner taking the plane including the polarization separation plane of the reflective polarization plate as a reference.
If, for example, there is adopted a support structure in which rotation around the virtual image center occurs when the support body is displaced from the desired position, the position of the principal ray (the pseudo principal ray) emitted in a pseudo manner from the virtual image center and entering perpendicularly the light entrance surface of the color combining optical device does not change. In other words, in the case of such a support configuration, no pixel shift occurs even if the support body is displaced from the desired position.
However, in the projector described in Document 1, since the support position is located at the position distant from the virtual image center as described above, it results that rotation around the position distant from the virtual image center easily occurs when the support body is displaced from the desired position.
In other words, it results that the amount of displacement of the pseudo principal ray due to the displacement of the support body is large, and as a result, the amount of pixel shift becomes large. Therefore, there arises a problem that it is difficult to form a preferable projection image.